ENVS 6611 Final Project Proposal

Author

Nissim Lebovits

Published

November 3, 2022

Summary

Using data from eBird, NOAA, and other relevant sources, this project will attempt to evaluate the possible impact of sea level rise on the spatial distribution of avifauna in the Philadelphia region.

Background

Study Area

Philadelphia sits at the boundary between the Atlantic Coastal Plain and Piedmont ecoregions. The area was historically covered with hardwood forests, but much of its natural vegetation has been removed for urbanization and cultivation.1 Built as a port along the Delaware River, the city was constructed on top of historic wetlands and mudflats. Due to infill and development, 95% of the region’s freshwater tidal wetlands have been lost. As a result of Philadelphia’s location and development patterns, SLR projections estimate that much of the area adjacent to the Delaware will be under water within the next century.2

The city of Philadelphia is also a major hotspot for bird biodiversity in North America. A key migratory stopover location on the Atlantic Flyway, Philadelphia sees more than 200 species of migratory birds pass through it each year.3 The city hosts a number of regional bird hotspots, especially Pennypack on the Delaware (266 species), John Heinz National Wildlife Reserve (281 species), and FDR Park (313 species).4 Given their proximity to the Schuylkill and Delaware rivers, all three of these sites are likely to be significantly impacted by SLR. From a management perspective, it is therefore important to understand the possible impact of SLR on Philadelphia’s avian biodiversity.

Bird Biodiversity Hotspots in the Philadelphia Region

Birds as Indicator Species

Birds are a popular subject for biodiversity monitoring because “compared to other vertebrates, birds are easily monitored by skilled observers and provide a mechanism to explore urban effects and responses to different urban designs.”5

“Bird populations are sensitive to many types of environmental change and, because they occupy a position at or near the top of the food chain, give indications of overall ecosystem functioning.”6

Existing Research

Research is lacking on the impacts of SLR on urban biodiversity in North America. While there is some literature on the impacts of SLR on tropical island biodiversity or on global extinction, there has not been much work done specifically on the impact of SLR on avifauna distributions, least of all in North American coastal cities.7 Generally speaking, however, a few general trends have been found. First, research suggests that species with limited ranges will be most impacted.8. In particular, species reliant on rare and/or vulnerable coastal habitats will be most threatened.9

Freshwater wetlands and intertidal habitats face especially high risk. Threats include increased levels of inundation and storm flooding; accelerated coastal erosion; sea water intrusion into freshwater tributaries; changes to the tidal prism, tidal range, sediment supply and rates of accretion; changes in air temperature and rainfall affecting the growth of salt marsh plants with secondary effects on sedimentation (Adam, 2002; Kennish, 2002; Moore, 1999; Nicholls et al., 1999; Reed, 1990).10 The effects of these inputs are unpredictable. For example, depending on a variety of factors, marshes could either contract or expand.11

Sea level rise will cause shifts in fl ooding potential on the urban coastal wetlands and beach zones, which will alter the habitat quality of these locations at rates signifi cantly above natural baseline conditions. The amount of sea level rise could have potential large-scale impacts on the areal extent and ecosystem health of the urban coastal wetlands, including permanent inundation, accelerated inland wetland migration (if the wetlands are not blocked by bulkheads or similar structures), and shifts in salinity gradients. (Urbanization, Biodiversity, and Ecosystem Services: Challenges and Opportunities*, Elmqvist et al., 2013, 497)

Project Goals

This report will combine NOAA sea level rise projections with eBird citizen science data on bird species presence to evaluate how Philadelphia’s endemic birds might be affected by future sea level rise. It will use a presence-only maximum entropy model, break species down by preferred habitat, and focus on endemic species listed by the IUCN as species of concern or higher.

Data

This project will draw on 3 key data sources:

  1. Bird observations recorded by eBird, a project of the Cornell Lab of Ornithology. CLO has published a guide to using eBird’s citizen science data for species distribution modeling, which I will be using extensively.
  2. The National Oceanic and Atmospheric Administration’s data on current sea levels and projected sea level rise.
  3. Various predictive factors assembled based on background reading and availability, such as habitat patch size, connectivity, degree of urbanization, road density, tree canopy cover, impervious surface cover, population density, land use, distance to fresh water, distance to salt water, etc.12 These layers will be assembled from ESRI, PASDA, and OpenDataPhilly, among other possible sources.

Challenges and Limitations

Because of the time frame of this assignment and my own limitations, this report will focus exclusively on sea level rise. Crucially, however, this is not an accurate representation of ecosystem function in the real world. It is impossible to divorce the impact of sea level rise alone on biodiversity from other confounding factors like coastal modification, saltwater intrusion, increased rainfall, and water pollution, let alone less proximate factors like changes in human population density and land use or the arrival of invasive species. Furthermore, as Pilkey and Pilkey point out, even if the scale of such impacts could be measured, it is difficult to account for ordering complexity: the unpredictable differences in impact depending on the order in which events occur.13 As Jimenez-Valverde et al., explain, prediction via species distribution modeling only works “if correlation structures are stable and consistent across different landscapes and time periods”.14 As a result, this project is more of an intellectual exercise than a genuine management tool. I will follow Pilkey and Pilkey, furthermore, in making only qualitative predictions based on my model (e.g., “the range of Species X will likely decrease”, or “species richness at FDR Park will likely decline”) rather than precise quantitative projections for species numbers or ranges.

Footnotes

  1. https://www.epa.gov/sites/default/files/2019-03/documents/phipa_final.pdf↩︎

  2. https://watercenter.sas.upenn.edu/philadelphia-urban-ecology-and-the-balance-of-human-and-ecological-communities/↩︎

  3. https://pa.audubon.org/chapters-centers/discovery-center↩︎

  4. https://ebird.org/hotspots↩︎

  5. Chace and Walsh, 1↩︎

  6. Wilby and Perry, 78↩︎

  7. include citations↩︎

  8. Urbanization, Biodiversity, and Ecosystem Services: Challenges and Opportunities, Elmqvist et al., 2013, 496↩︎

  9. Wilby and Perry (2006), 73↩︎

  10. From Wilby and Perry 76↩︎

  11. Wilby and Perry 76-78↩︎

  12. Ecology and Conservation of Birds in Urban Environments, Murgui and Hedblom eds., 2017↩︎

  13. Useless Arithmetic, 2007↩︎

  14. Jimenez-Valverde et al., 2009↩︎